The incidence of smoking among pregnant women remains significant despite the efforts of public health campaigns to inform the population as to the detrimental effects of smoking. Many health risks for the fetus are associated with smoking during pregnancy including an increased incidence of Attention Deficit Disorders and sudden infant death syndrome (SIDS). The hypothesis underlying the work outlined in this proposal is that impaired or delayed maturation of the circadian systems plays a role in the occurrence of SIDS and that prenatal insults which impact on the normal development of this system increases the likelihood of SIDS. Clegg et al. (in press) have found that prenatal nicotine exposure in rat pups induces expression of the DNA binding protein c-fos in the fetal, but not the maternal suprachiasmatic nucleus (SCN). Induction of c-fos mRNA in the adult SCN by light exposure has been associated with phase-shifts of the circadian system. These results suggest that nicotine exposure may induce a desynchrony between the circadian time keeping system of the mother and the fetus. I propose to further elucidate the changes in neural gene expression in the SCN that occurs as a consequence of prenatal nicotine exposure and study the functional consequences of this exposure.